The Food and Drug Administration (FDA) has approved the drug cemiplimab (Libtayo) for patients with an advanced form of cutaneous squamous cell carcinoma (SCC), a common type of skin cancer. This is the first agent to be approved by FDA specifically for advanced SCC.

Approval Based on Results of Two Clinical Trials

Although squamous cell carcinoma of the skin is common, it is rare for the cancer to spread, or metastasize, to distant parts of the body. Surgery can cure earlier stages of SCC in more than 95% of patients.

SCC begins in cells that form the outer layer of the skin, usually in areas that have been exposed to natural or artificial sunlight, such as from tanning beds, over long periods of time. Advanced SCC may cause disfigurement and may become life-threatening if it spreads to other parts of the body.

FDA’s approval of cemiplimab was based on the results of two early-phase clinical trials involving 108 patients (75 with metastatic disease and 33 with locally advanced disease). In one of the trials, 13 of 26 patients responded to cemiplimab.

In the second trial, 28 of 59 patients with metastatic disease who were treated with cemiplimab had their tumors shrink or disappear.

Among the 28 patients with metastatic disease who had a response, 16 had responses that lasted longer than 6 months, and 13 of these continued to have a response and to receive cemiplimab when the analysis ended.

By comparison, only about 15%–25% of patients with advanced SCC respond to the chemotherapy regimens or targeted therapies that are sometimes used to treat the disease, and many experience debilitating side effects from these treatments, explained Michael Migden, M.D., of the University of Texas MD Anderson Cancer Center, who led the clinical trials.

The trial was funded by Regeneron Pharmaceuticals, which invented cemiplimab, and Sanofi, which will help to market the drug. Patients with advanced SCC were the first to receive cemiplimab.

Other checkpoint inhibitors are now being evaluated in patients with this rare cancer, and cemiplimab is being tested for patients with other types of cancer, according to Dr. Korde.

Common side effects of cemiplimab include fatigue, rash, and diarrhea. The drug can also cause the immune system to attack normal organs and tissues in the body. In some cases, these reactions can be severe and may be life threatening.

“As with any other immunotherapy drug on the market, there can be significant side effects from treatment with cemiplimab,” said Dr. Korde. “Any treatment decision should be made by physicians and patients working together.”

Testing an Immunotherapy Drug

The researchers decided to test a checkpoint inhibitor in advanced SCC for two reasons. First, these cancers tend to have a high number of genetic mutations (i.e., they are hypermutated), likely because of the exposure to ultraviolet radiation. Known as a high tumor mutational burden, this condition has been associated with a response to immunotherapy in some other types of cancer.

In addition, the risk of SCC is much higher in individuals whose immune system and ability to fight infections and other diseases have been suppressed as a result of illness or treatment for disease than in people whose immune systems function normally. This observation suggested to the researchers that strengthening the body’s immune response against tumor cells might be an effective strategy for treating the disease.

More research is needed to identify the best treatment for patients with advanced SCC, noted Dr. Korde. “But the current study is moving in the right direction, and we are hopeful that future studies will lead to the discovery of additional treatments for this disease.”

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